It has long been known that nicotine is a component of various tobacco products that contributes to addiction. The art is rich with methods for administering nicotine to humans without the use of tobacco. These tobacco-free nicotine administrations are designed to reduce human dependence on tobacco products. Some of the tobacco-free nicotine administration methods include transdermal patches or confectionary products such as lozenges. Another well-known method for administering nicotine without tobacco use is the use of chewing gum. Examples of nicotine chewing gums can be found in U.S. Pat. Nos. 3,845,217; 3,877,468; 3,901,248; 5,488,962 and 6,344,222 and Patent Cooperation Treaty Publication No. WO 2007/053096. Nicotine chewing gums are also commercially available under the trade names NICORETTE® and THRIVE®. These prior art nicotine chewing gums may be prepared with hydrophilic liquid plasticizers or solvents such as glycerin, propylene glycol, or ethanol. These hydrophilic liquids, even in small amounts, can promote the degradation of nicotine to undesirable impurities.
Nicotine, or 3-(1-methyl-2-pyrrolidinyl)pyridine, is a tertiary amine with the following structure:

Under ambient conditions, nicotine is an oily, volatile, hygroscopic liquid that is sensitive to light and air. Nicotine's chemical and physical properties present a number of processing and stability issues. For example, because nicotine is volatile, it may evaporate during its incorporation into an administration vehicle such as a gum or lozenge. In addition, the nitrogen in the pyrrolidinic ring can undergo protonation in the presence of an acid. Nicotine free base is labile to oxidation through an electrophilic attack.
Some of the components that may be used in nicotine gums contain non-bonded electron pairs which tend to promote and/or facilitate the unwanted oxidation of the nicotine free base present in nicotine chewing gum. When the ingredients with non-bonded electron pairs are in liquid form, even in relatively small concentrations, the pyrrolidinic nitrogen in the nicotine molecule is more prone to oxidation and unwanted degradation.
In an effort to reduce the processing and stability issues associated with the nicotine compound, a number of nicotine complexes have been described in the art. For example, U.S. Pat. No. 5,512,306 employs a complex of cyclodextrin and nicotine to prepare smoking substitutes such as tablets and powders. A more common method involves the preparation of a complex of nicotine and an ion exchange resin. Nicotine ion exchange complexes are described in U.S. Pat. Nos. 3,845,217; 3,877,468; and 3,901,468, which are incorporated herein by reference. A well-known complex that is currently used in the commercially-available nicotine chewing gums is nicotine polacrilex which is a complex of nicotine and the cation exchange resin AMBERLITE 164.
Although the aforementioned nicotine complexes have improved the processing and stability of nicotine, they have not completely solved the problems. For example, these complexes retain some nicotine free base. The residual nicotine free base is prone to oxidation especially when in the presence of liquids with non-bonded electron pairs, especially liquids with hydroxide moieties.
It is therefore an object of the present invention to provide a nicotine-containing chewing gum having improved stability.
It is a further object of the present invention to provide a nicotine containing chewing gum that has a longer shelf life than the currently available nicotine chewing gums.
It is also an object of the present invention to provide a nicotine containing chewing gum that exhibits reduced levels of trans-Nicotine-N-oxide and cis-Nicotine-N-Oxide upon storage.
It is an additional object of the present invention to provide a nicotine chewing gum that is prepared without a liquid that contains non-bonded electron pairs, preferably without liquids that contain hydroxyl moieties.
It is also an additional object of the present invention to provide a nicotine containing chewing gum that is prepared with only hydrophobic liquids.
It is another object of the present invention to provide a nicotine containing chewing gum that is prepared with little or no hydrophilic liquids.
These and other objects of the present invention will become apparent from a review of the appended specification.